He was prominently featured as himself in the "scroll" (first draft) version of Jack Kerouac's novel On the Road, and served as the model for the character Dean Moriarty in the 1957 version of that book. In many of Kerouac's later books, Cassady is represented by the character Cody Pomeray. Cassady also appeared in Allen Ginsberg's poems, and in several other works of literature by other writers.

As a youth, Cassady was repeatedly involved in petty crime. He was arrested for car theft when he was 14, for shoplifting and car theft when he was 15, and for car theft and fencing stolen property when he was 16.

In 1941, the 15-year-old Cassady met Justin W. Brierly, a prominent Denver educator.[4] Brierly was well known as a mentor of promising young men and was impressed by Cassady's intelligence. Over the next few years, Brierly took an active role in Cassady's life. Brierly helped admit Cassady to East High School where he taught Cassady as a student, encouraged and supervised his reading, and found employment for him. Cassady continued his criminal activities, however, and was repeatedly arrested from 1942 to 1944; on at least one of these occasions, he was released by law enforcement into Brierly's safekeeping. In June 1944, Cassady was arrested for possession of stolen goods and served eleven months of a one-year prison sentence. He and Brierly actively exchanged letters during this period, even through Cassady's intermittent incarcerations; this correspondence represents Cassady's earliest surviving letters.[5] Brierly, a closeted homosexual, is also believed to have been responsible for Cassady's first homosexual experience.[6]

In October 1945, after being released from prison, Cassady married the 16-year-old LuAnne Henderson.[7] In 1946, the couple traveled to New York City to visit their friend, Hal Chase, another protégé of Brierly's. It was while visiting Chase at Columbia University that Cassady met Jack Kerouac and Allen Ginsberg.[8] Although Cassady did not attend Columbia, he soon became friends with them and their acquaintances, some of whom later became members of the Beat Generation. While in New York, Cassady persuaded Kerouac to teach him to write fiction. Cassady's second wife, Carolyn, has stated that, "Neal, having been raised in the slums of Denver amongst the world's lost men, [was] determined to make more of himself, to become somebody, to be worthy and respected. His genius mind absorbed every book he could find, whether literature, philosophy or science. Jack had a formal education, which Neal envied, but intellectually he was more than a match for Jack, and they enjoyed long discussions on every subject." [9]

Carolyn Robinson met Cassady in 1947, while she was studying for her Masters in Theater Arts at the University of Denver.[10] Five weeks after LuAnne's departure, Neal got an annulment from LuAnne and married Carolyn, on April 1, 1948. Carolyn's book, Off the Road: Twenty Years with Cassady, Kerouac and Ginsberg (1990), details her marriage to Cassady and recalls him as, "the archetype of the American Man".[11] Cassady's sexual relationship with Ginsberg lasted off and on for the next 20 years.[12]

During this period, Cassady worked for the Southern Pacific Railroad and kept in touch with his "Beat" acquaintances, even as they became increasingly different philosophically.

The couple eventually had three children and settled down in a ranch house in Monte Sereno, California, 50 miles south of San Francisco, where Kerouac and Ginsberg sometimes visited.[13] This home, built in 1954 with money from a settlement from Southern Pacific Railroad for a train-related accident, was demolished in August 1997.[14]
In 1950, Cassady entered into a bigamous marriage with Diane Hansen, a young model who was pregnant with his child, Curtis Hansen.[15]

Cassady traveled cross-country with both Kerouac and Ginsberg on multiple occasions, including the trips documented in Kerouac's On the Road.

Following an arrest in 1958 for offering to share a small amount of marijuana with an undercover agent at a San Francisco nightclub, Cassady served a two-year sentence at California's San Quentin State Prison in Marin County. After his release in June 1960, he struggled to meet family obligations, and Carolyn divorced him when his parole period expired in 1963. Carolyn stated that she was looking to relieve Cassady of the burden of supporting a family, but "this was a mistake and removed the last pillar of his self-esteem".[16]

After the divorce, in 1963, Cassady shared an apartment with Allen Ginsberg and Beat poet Charles Plymell, at 1403 Gough Street, San Francisco.

Cassady first met author Ken Kesey during the summer of 1962; he eventually became one of the Merry Pranksters, a group who formed around Kesey in 1964 who were vocal proponents of the use of psychedelic drugs.

In January 1967, Cassady traveled to Mexico with fellow prankster George "Barely Visible" Walker and Cassady's longtime girlfriend Anne Murphy. In a beachside house just south of Puerto Vallarta, Jalisco, they were joined by Barbara Wilson and Walter Cox. All-night storytelling, speed drives in Walker's Lotus Elan, and the use of LSD made for a classic Cassady performance — "like a trained bear," Carolyn Cassady once said. Cassady was beloved for his ability to inspire others to love life. Yet at rare times he was known to express regret over his wild life, especially as it affected his family. At one point Cassady took Cox, then 19, aside and told him; "twenty years of fast living—there's just not much left, and my kids are all screwed up. Don't do what I have done."

During the next year, Cassady's life became less stable, and the pace of his travels more frenetic. He left Mexico in May, traveling to San Francisco, Denver, New York City, and points in between. Cassady then returned to Mexico in September and October (stopping in San Antonio, on the way to visit his oldest daughter who had just given birth to his first grandchild), visited Ken Kesey's Oregon farm in December, and spent the New Year with Carolyn at a friend's house near San Francisco. Finally, in late January 1968, Cassady returned to Mexico once again.

On February 3, 1968, Cassady attended a wedding party in San Miguel de Allende, Guanajuato, Mexico. After the party, he went walking along a railroad track to reach the next town, but passed out in the cold and rainy night wearing nothing but a T-shirt and jeans. In the morning, he was found in a coma by the tracks, reportedly by Anton Black, later a professor at El Paso Community College, who carried Cassady over his shoulders to the local post office building. Cassady was then transported to the closest hospital where he died a few hours later on February 4, four days short of his 42nd birthday.

The exact cause of Cassady's death remains uncertain. Those who attended the wedding party confirm that he took an unknown quantity of secobarbital, a powerful barbiturate sold under the brand name Seconal. The physician who performed the autopsy wrote simply, "general congestion in all systems." When interviewed later, the physician stated that he was unable to give an accurate report because Cassady was a foreigner and there were drugs involved. "Exposure" is commonly cited as his cause of death, although his widow believes he may have died of renal failure.[17]

Cassady has five known children: Robert William Hyatt Jr. (1945), Cathleen Joanne Cassady (1948), Jami Cassady Ratto (1949), Curtis W. Hansen (1950), and John Allen Cassady (1951). Robert, son of Neal Cassady and Maxine Beam, is an artist working in Arvada, Colorado. In February 2017, he was featured in Westword Magazine.[18] Cathleen, known as Cathy, is the mother of the only grandchild Neal met. Cathy, Jami, and John keep a website in memory of their parents and parents' "beat" friends.[19][20]

Curt, born from a bigamous marriage with Diana Hansen, died April 30, 2014, aged 63. He was one of the co-founders of radio station WEBE 108, in Bridgeport, Connecticut.[21]

Cassady is credited with helping Kerouac break with his Thomas Wolfe-influenced sentimental style, as seen in The Town and the City (1950). After reading Cassady's letters, Kerouac was inspired to write his story in Cassady's communication style: "...in a rush of mad ecstasy, without self-consciousness or mental hesitation".[22]

This fluid writing style, reading more like a stream of consciousness or hypermanic rapid-fire conversation than written prose, is best demonstrated within Cassady's letters to family and friends. In a letter to Kerouac from 1953, Cassady begins with the following fervent sentence;

Well it's about time you wrote, I was fearing you farted out on top that mean mountain or slid under while pissing in Pismo, beach of flowers, food and foolishness, but I knew the fear was ill-founded for balancing it in my thoughts of you, much stronger and valid if you weren't dead, was a realization of the experiences you would be having down there, rail, home, and the most important, climate, by a remembrance of my own feelings and thoughts (former low, or more exactly, nostalgic and unreal; latter hi) as, for example, I too seemed to spend time looking out upper floor windows at sparse, especially night times, traffic in females—old or young.[23]

On the Road became a sensation. By capturing Cassady's voice, Kerouac discovered a unique style of his own that he called "spontaneous prose," a stream of consciousness prose form.[24]

Cassady's own written work was never formally published in his lifetime, and he left behind only a half-written manuscript and a number of personal letters. Cassady admitted to Kerouac in a letter from 1948, "My prose has no individual style as such, but is rather an unspoken and still unexpressed groping toward the personal. There is something there that wants to come out; something of my own that must be said. Yet, perhaps, words are not the way for me." [23]

Love Always, Carolyn — A film about Kerouac, Cassady and Me (2011), a documentary that features Cassady in archival segments, as well as interviews with Cassady's ex-wife Carolyn and his children.[25]

Magic Trip (2011), Alex Gibney's documentary film using the footage shot by Ken Kesey and the Merry Pranksters during their cross-country bus trip in the Furthur bus; the hyperkinetic Cassady is frequently seen driving the bus, jabbering, and sitting next to a sign that boasts, "Neal gets things done."

The film Who'll Stop the Rain (1978) is a psychological drama released by United Artists. The film is based on Robert Stone's novel Dog Soldiers (1974), and stars Nick Nolte as Ray Hicks. Stone based the character of Hicks on Beat writer Neal Cassady. Stone became acquainted with Cassady through novelist Ken Kesey, a classmate of Stone's in graduate school at Stanford University. Hicks' death scene on the railroad tracks at the film's conclusion was directly based on Cassady's death along a railroad track outside of San Miguel de Allende, Mexico, in 1968.

Heart Beat (1980), which portrays Neal Cassady's friendship with Jack Kerouac, stars Nick Nolte as Cassady and John Heard as Kerouac. The film was based on the memoir of the same name by Carolyn Cassady (played by Sissy Spacek). Talk show host Steve Allen, who was a big supporter of On The Road, appears briefly as himself. Released immediately after Warner Bros. acquired Orion Pictures, the film was given a limited release due to studio politics and a perceived lack of public interest. The film quickly fell from view.

What Happened to Kerouac (1986).

The Last Time I Committed Suicide (1997), with Thomas Jane as Cassady, is based on the "Joan Anderson letter" written by Cassady to Jack Kerouac in December 1950. Until 2014, much of this letter was thought to have been lost, though an excerpt had been published in a 1964 edition of John Bryan's magazine Notes from Underground.

Neal Cassady (2007), a biographical film [28] focused mostly on the Merry Prankster years and stars Tate Donovan as Neal, Amy Ryan as Carolyn Cassady, Chris Bauer as Kesey, and Glenn Fitzgerald as Kerouac; Noah Buschel wrote and directed the film, which deals primarily with how Neal became trapped by his fictional alter-ego, Dean Moriarty. The Cassady family criticized this film as highly inaccurate.[29]

On the Road (1957) as "Dean Moriarty". Cassady was the model for the character Dean Moriarty in Kerouac's On the Road, and the character "Cody Pomeray" in many of Kerouac's other novels. In the surviving first draft of On the Road, which Kerouac typed on a 120-foot roll of paper specially constructed for that purpose, the story's protagonist's name remains "Neal Cassady".[33] However, in Kerouac's final edition of On The Road, Cassady's character is known as "Dean Moriarty". In On the Road, the narrator, Sal Paradise (representing Jack Kerouac) states, "He was simply a youth tremendously excited with life, and though he was a con-man, he was only conning because he wanted so much to live and to get involved with people who would otherwise pay no attention to him ... Somewhere along the line, I knew there'd be girls, visions, everything; somewhere along the line, the pearl would be handed to me."[34]

Kesey also wrote a fictional account of Cassady's death in the short story "The Day After Superman Died" (1979, referring to Cassady as "Houlihan"), wherein Cassady is portrayed as mumbling about the number of railroad ties he had counted on the line (64,928) as his last words before dying. It was published as a part of Kesey's collection Demon Box (1986).

In Hunter S. Thompson's book Hell's Angels (1966), Cassady is described as, "the worldly inspiration for the protagonist of two recent novels", drunkenly yelling at police during the famed Hells Angels parties at Ken Kesey's residence in La Honda, California. Although Cassady's name was removed from the book at the insistence of Thompson's publisher, the description is clearly a reference to the character based on Cassady in Jack Kerouac's works, On the Road and Visions of Cody (1951–1952).

A second Grateful Dead song, "Cassidy" by John Perry Barlow, might seem to be a misspelling of Cassady's name. However, in fact, the song primarily celebrates the 1970 birth of baby girl Cassidy Law into the Grateful Dead family, though the lyrics also include references to Neal Cassady himself.[38]

"The Joan Anderson Letter", written by Cassady to Jack Kerouac (December, 1950): it was until 2014, thought to have been lost, though an excerpt had been published in a 1964 edition of John Bryan's magazine Notes from Underground.[39] Associated Press reported in November 24, 2014, that the entire letter had been found. The 18-page letter, which is said to have substantially inspired Kerouac's subsequent writing style, was to be auctioned on December 17, 2014, but a legal dispute over ownership prevented the auction from proceeding.[40][41] The original letter was auctioned by Heritage Auctions as Lot 45378 on March 8, 2017.[42][43][44]

^Turner 1996, p. 79 ("Brierly had been sexually attracted to Neal, and managed to entice him into his first homosexual experience.");Sandison & Vickers 2006, pp. 41–42 ("Brierly was most likely also a closet homosexual, and it was probably through him that Neal Cassady would first discover and explore gay sex and serve as a hustler in Denver's gay community.") According to some reports, however, Brierly's sexual orientation was an open secret. See Weir, John (2005-06-22), "Everybody knows, nobody cares, or: Neal Cassady's Penis", TriQuarterly, archived from the original on 2009-06-20.